Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.
As telephone and data networks converge towards common technology, new protocols are emerging that allow terminals to establish person-to-person communication sessions over data networks. These new protocols represent an alternative to the ones by which calls are established over conventional telephone networks, allowing those networks to be phased out. Operators of telephone networks have invested in technology required to support these protocols, specifically the 3GPP IP Multimedia Subsystem (IMS), which supports the IETF Session Initiation Protocol (SIP) standard. Alternative communication protocols are already in widespread use in the Internet for Instant Messaging and Presence Services (IMPS) and standards are emerging, specifically the Extensible Messaging and Presence Protocol (XMPP).
The SIP and XMPP standards define general purpose session control protocols that do not restrict the media used in the session. Despite this flexibility, individual SIP or XMPP applications tend to focus on one particular kind of session, such as text message chat (Instant Messaging) or a particular game. As a result the user experience tends to involve many distinct, unrelated applications, and the user must decide which to use for each kind of session. It is widely thought that customers are overwhelmed with the complexities of using such a large number of applications, and hence commercial uptake would be hindered.
A particular challenge faced by users of conventional applications is that, in order to change the kind of session they are in, they must change applications; from an IM application to a game, for example. As each application presents the user with its own set of concepts and controls, and manages its own set of sessions, the transition is not particularly smooth for the participants of the session. Furthermore, the user must manually re-establish the original session in the new application, even when the new session involves the same set of participants.
Another challenge faced by users of communication applications is that all participants in a particular kind of session must have the appropriate application installed on their terminal. Requiring all participants to already have the same application before a session can start severely limits spontaneity. This requirement is a major barrier to the adoption of new services, as demonstrated by the relatively slow take up of the Multimedia Messaging Service and Video Telephony.
These challenges are not faced by people in a real world conversation. For example: people might start talking, then look through some photographs together, and then start playing a game. In face-to-face situations parties may spontaneously include many forms of media in the conversation to enrich it. At a conceptual level the common thread is the conversation, not the media being used within it. This concept is often lost in the conventional approach to SIP or XMPP applications.
Some personal computer applications allow conference sessions to be established where any party is able to share many other applications with other parties even if those other parties do not have those applications installed. However, these conferencing applications require a reliable, high-bandwidth network connection, the capacity to store relatively large amounts of application data, and typically a large screen area and a pointing device. Known approaches along such lines are not suitable for communication sessions using handheld terminals, given that handheld terminals have relatively limited network, memory, processor, display, and input capabilities.